A simple variable lift and/or timing valving arrangement for a twin intake (and/or exhaust) valved engine has long been desirable. At idle and relatively low loads, it is desirable to move the valves to a relatively low opened position (low lift) and for a relatively short duration for increasing the flow velocity of air entering a cylinder. This promotes a thorough mixing of air and fuel and provides a more complete combustion. At mid-level engine speeds with moderate loading, an increased opening (lift) of the valves and/or a longer opening duration is desirable to adequately meet the air and fuel needs of the engine. At greater engine speeds and/or greater loading of the engine, increased opening or lift of the valves and/or opening duration is desirable. At wide open throttle, it is desirable to increase again the opening of the valves and increase the opening duration to provide maximum power for the engine.
A preexamination patent search of the subject valve train arrangement uncovered U.S. patents: U.S. Pat. No. 4,727,830 to Nagahiro et. al.; U.S. Pat. No. 4,759,322 to Konno; U.S. Pat. No. 4,777,914 to Konno; U.S. Pat. No. 4,788,946 to Inoue et. al.; U.S. Pat. No. 4,793,296 to Inoue et. al.; U.S. Pat. No. 4,869,214 to Inoue et. al.; U.S. Pat. No. 4,887,563 to Ishida et. al.; U.S. Pat. No. 4,905,639 to Konno; and U.S. Pat. No. 5,031,583 to Konno which disclose valve train arrangements with modes of operation using three rocker arms arranged side by side and a camshaft with three lobes for each cylinder. The rocker arm located between two end rocker arms houses a pair of pistons within bores formed through each of its side surfaces which face the other rocker arms. A bore in the other rocker arms receives a piston which is selectively moveable out from the bore of the middle rocker arm. A pair of passages in the middle rocker arm selectively pressurize a space behind each of the pistons to cause movement of the piston. The U.S. Pat. No. 4,799,463 is similar to the above described patents except that four rocker arms are provided rather than three.
U.S. Pat. No. 4,768,475 to Ikemura discloses a valve train mechanism for a single intake valve type cylinder head utilizing a pair of rocker arms activated by a two lobed per cylinder camshaft. Multiple pins within aligned bores formed in one of the rocker arms and in an actuating arm are selectively moved to link the members together.
U.S. Pat. No. 5,033,420 to Matayoshi et. al. discloses a valve structure including pivots formed in the cylinder head and a hydraulic fluid supply passage to said pivot with an adjustment screw and passage therein.
U.S. Pat. No. 5,042,437 to Sakuragi discloses a valve train arrangement with a single rocker arm supporting several cam follower which are selectively retractable away from a respective cam lobe.